Sapling tree to a mesh and follow the treeArm Animation like the leaves?
I had this exact problem, and I just found out the solution. In the Operator panel for the Sapling, simply check the "Make Mesh" box in the Armature menu and there you go! If you want to edit the mesh, you have to look for the Skin modifier that is created in the Outline under's the tree's mesh and apply it.

Hope this solves your problem!